Identification and quantification by LC-MS and LC-ICP MS of arsenic species in urine of rats chronically exposed to dimethylarsinic acid (DMAA)

The potential of liquid chromatography-mass spectrometry (LC-MS) using elec trospray ionization (ESI) was investigated for the identification and quant ification of organoarsenic species excreted in rats urine chronically expos ed to dimethylarsinic acid (DMAA). Quantification was performed by both LC- ESI-MS and LC-inductively coupled plasma mass spectrometry (ICP-MS), The de tection limits of organoarsenic species in LC-ESI-MS with cation-exchange c hromatography were 75-200 pg as arsenic. Although there are about ten times higher than that of LC-ICP-MS, LC-ESI-MS had a low enough detection limit to determine major metabolic arsenic species in the urine. LC-ESI-MS was ap plied to the identification of organoarsenic species in the urine. Major ar senic peaks in urine were identified as DMAA and trimethylarsine oxide usin g agreement of the spectra and retention times. Three unidentified arsenic peaks were found in the urine; one of these was determined to be tetramethy larsonium ion by agreement of both the spectrum and the retention time. LC- ESI-MS and LC-ICP-MS were also used to quantify organoarsenic: in urine: go od agreement between LC-ESI-MS and LC-ICP-MS was obtained. Copyright (C) 19 99 John Wiley & Sons, Ltd.